Many patients that suffer from congestive heart failure (CHF) develop a wide QRS complex resulting from a delayed activation of one of the ventricles in the heart, and inter-and/or intraventricular electro-mechanical dysynchrony. This ventricular “dysynchrony” may be caused by dilation of the heart, which disrupts the conductive pathways and interferes with depolarization sequences. Ventricular dysynchrony may worsen heart failure symptoms.
In a classic case of ventricular dysynchrony, the patient's right ventricle activates first, and the left ventricle activates at a later time. The patient often experiences a reduction in cardiac output because the ventricles begin contraction at significantly different times. The timing imbalance may also cause the patient to experience paradoxical septal motion, mitral regurgitation or decreased ventricular filling time.
Patients having a wide QRS complex or having inter- and/or intraventricular electro-mechanical dysynchrony may receive benefits from an implanted medical device, such as a pacemaker, that paces both ventricles. The implanted medical device senses or paces atrial contractions, waits a predetermined time (or atrioventricular (AV) delay) after each sensed or paced atrial contraction, and then paces both ventricles. The ventricles may be paced simultaneously, or one ventricle may be paced before another. This bi-ventricular pacing is one form of cardiac resynchronization, and it provides many CHF patients with improvements in quality of life, exercise capacity and overall cardiac function.
Generally speaking, cardiac resynchronization refers to pacing therapies applied by implanted medical devices with pacing leads in two or more complementary chambers of the heart, i.e., the atria or the ventricles. In response to a sensed or paced event, the pacemaker delivers pacing pulses or stimulations to two complementary chambers of the heart. The pacing pulses may be, but need not be, delivered simultaneously.
Many pacemakers, including pacemakers that provide cardiac resynchronization, may monitor cardiac rhythms for various forms of arrhythmia. In general, when a pacemaker senses a potential arrhythmia, the pacemaker may execute specialized classification algorithms. In this way, the pacemaker can discriminate between or among various heart rhythms and can classify arrhythmias according to type.
In some patients, such as patients that receive multiple-chamber pacing, several sensors may be implanted in or around the patient's heart. In addition to the pacing electrodes of the pacemaker, which also sense electrical activity, the patient may receive one or more sensors that respond to other conditions. For example, the patient may receive a pressure sensor. A pressure sensor may be useful in monitoring conditions that may accompany heart failure, such as cardiac decompensation.
Multiple-chamber pacing systems in general, and bi-ventricular and bi-atrial pacing systems in particular, are known in the art. Techniques for classification of various arrhythmias are likewise known in the art. In addition, use of sensors such as pressure sensors, including use of pressure sensors with multiple-chamber pacing systems, is also known in the art. There is a need, however, for useful coordination of these techniques. In addition, some of these techniques may involve implantation of multiple electrodes or other sensors, which can be difficult and time-consuming.
Examples of these techniques and/or devices may be found in the issued U.S. Patents listed in Table 1 below.
TABLE 1U.S. Pat. No.InventorIssue Date3,857,399ZacoutoDec. 31, 19744,730,619Koning et al.Mar. 15, 19884,802,481SchroeppelFeb. 07, 19894,928,688MowerMay 29, 19905,119,813CohenJun. 09, 19925,540,727Tockman et al.Jul. 30, 19965,584,868Salo et al.Dec. 17, 19965,626,623Kieval et al.May 06, 19975,728,140Salo et al.Mar. 17, 19986,021,350MathsonFeb. 01, 2000
All patents listed in Table 1 above are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments and claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the techniques of the present invention.